1. Field of the Invention
The invention relates to an objective adjustment for rifle scope collimation and more particularly to a linear adjustment for use with scopes having a non-circular objective end.
2. Description of the Prior Art
In conventional rifle scopes, the adjustment of the objective lens system for collimation is accomplished by providing threads on the inside of the outer housing of the scope at the outer end thereof which receive corresponding threads on the outer surface of a lens mount containing the objective lens. To adjust the back focal position of the objective lens system to coincide with the focal point of the remaining lens systems, the lens mount together with the objective lens system is rotated whereby the pitch of the threads causes the objective lens system and the mount to move forwardly or rearwardly of the outer housing until the appropriate position is reached.
Obviously such an adjustment system is of no use for scopes in which the objective end is not circular because rotational movement is impossible. Furthermore, even with a circular objective lens there are certain disadvantages. If the mechanical axis of the lens mount is not coincident with the optical axis of the rifle scope, the image moves in relation to the remaining system and the reticle position. Thus, after positioning the objective lens system, the reticle must be adjusted to the optical center of the scope.